The invention relates to novel amides of L-aspartyl-D-alanine, L-aspartyl-D-serine, L-aspartyl-D-2-aminobutyric acid, L-aspartyl-D-valine and L-aspartyl-D-2-aminopentanoic acid which are especially useful in view of their potent sweetening properties, novel methods for their use in foods and edible compositions containing them.
In U.S. 3,492,131 certain lower alkyl esters of L-aspartyl-L-phenylaline were found to be up to 200 times as sweet as sucrose and to be substantially free of bitter flavor notes which detracted from earlier artificial sweeteners such as saccharin. These compounds were subsequently found to have only limited stability in aqueous systems due to diketopiperazine formation, especially at the neutral-acid pH conditions prevalent in most food systems, and hydrolysis of the ester group at low pH.
Mazur et al., J. Med. Chem., 16, 1284 (1973) have disclosed that lower alkyl esters of L-aspartyl-D-alanine and certain homologs thereof, especially L-aspartyl-D-alanine isopropyl ester, have sweetness potencies of up to 125 times sucrose.
Sukehiro et al., Seikatsu Kagaku, 11, 9-16 (1977); Chem. Abstr., 87, 168407h (1977) have disclosed certain amides of L-aspartyl-D-alanine of the formula ##STR3## where R.sup.1 is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, cyclohexyl or the carbon residue of the methyl esters of glycine, d-alanine or 1-alanine. The most potent compounds were those wherein R.sup.1 is one of the above butyl groups or cyclohexyl, having respectively, 100-125 and 100 times the sweetness of sucrose. Since the n-butylamide was found to have 125 times the sweetness of sucrose and the isobutyl and secondary butyl amides are 100.times.sucrose, it was concluded that the potency of these amides is affected mainly by the number of carbon atoms in the alkyl group, R.sup.1, and that structural isomerism in the alkyl group has little effect on the sweetness potency.